Theoretical investigation of the electronic and optical properties of oligothiophenes upon methyl, thiol, and thiomethyl substitutions

The geometric, electronic, and optical properties of oligothiophenes of 2, 4, 6 and 8 units of head-to-head–tail-to-tail (HH–TT) regioselectivity and substituted by methyl, thiol, and thiomethyl groups have been characterized in their neutral and p-doped states with quantum-chemical calculations derived from semiempirical Hartree–Fock approaches and with the nonempirical valence effective Hamiltonian (VEH) method. Such calculations provide a good insight into the electronic properties measured for electropolymerized chains.